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921.
Miomandre F Meallet-Renault R Vachon JJ Pansu RB Audebert P 《Chemical communications (Cambridge, England)》2008,(16):1913-1915
The first-time coupling of fluorescence microscopy with a three-electrode electrochemical cell is described and applied to the investigation of a controlled-potential redox switch of organic fluorophores such as tetrazine derivatives. 相似文献
922.
Lee JK Fuchter MJ Williamson RM Leeke GA Bush EJ McConvey IF Saubern S Ryan JH Holmes AB 《Chemical communications (Cambridge, England)》2008,(39):4780-4782
A high yielding, batch mode synthesis of diaryl ethers and sulfides by an S(N)Ar fluoride-mediated process in scCO(2) has been developed; the use of a polymer-supported imidazolium fluoride reagent in batch mode led to the development of a fixed-bed continuous flow process, with high conversions. 相似文献
923.
Geramita K McBee J Tao Y Segalman RA Tilley TD 《Chemical communications (Cambridge, England)》2008,(41):5107-5109
The synthesis, optical, electrochemical and physical characterization of 2,7-bis(pentafluorophenylethynyl)hexafluoroheterofluorenes is described along with a preliminary evaluation of their performance in photovoltaic applications. 相似文献
924.
The rate constants for the reactions of atomic bromine with dimethyl ether and diethyl ether were measured from approximately 300 to 350 K using the relative rate method. Both isooctane and isobutane were used as the reference reactants, and the rate constants for the reactions of these hydrocarbons were measured relative to each other over the same temperature range. The kinetic measurements were made by photolysis of dilute mixtures of bromine, the reference reactant, and the test reactant in mixtures of argon and oxygen at a total pressure of 1 atm. The resulting ratios of rate constants were combined with the absolute rate constant as a function of temperature for the reference reaction of Br with isobutane to calculate absolute rate constants for the reactions of Br with isooctane, dimethyl ether, and diethyl ether. The absolute rate constant, in the units cm3 molecule(-1) s(-1), for the reaction of Br with dimethyl ether was given by k = (3.8 +/- 2.4) x 10(-10) exp(-(3.54 +/- 0.21) x 10(3)/T) while for the reaction of Br with diethyl ether the rate constant is given by k = (2.8 +/- 2.7) x 10(-10) exp(-(2.44 +/- 0.32) x 10(3)/T). On the same basis, the rate constant for the reaction of Br with isooctane is given by k = (3.34 +/- 0.59) x 10(-12) exp(-(1.80 +/- 0.11) x 10(3)/T). In each case, the activation energy of the reaction is significantly smaller than the endothermicity of the reaction. This is discussed in terms of a complex mechanism for these reactions. 相似文献
925.
926.
927.
Schell U Haydock SF Kaja AL Carletti I Lill RE Read E Sheehan LS Low L Fernandez MJ Grolle F McArthur HA Sheridan RM Leadlay PF Wilkinson B Gaisser S 《Organic & biomolecular chemistry》2008,6(18):3315-3327
The glycosylation of natural product scaffolds with highly modified deoxysugars is often essential for their biological activity, being responsible for specific contacts to molecular targets and significantly affecting their pharmacokinetic properties. In order to provide tools for the targeted alteration of natural product glycosylation patterns, significant strides have been made to understand the biosynthesis of activated deoxysugars and their transfer. We report here efforts towards the production of plasmid-borne biosynthetic gene cassettes capable of producing TDP-activated forms of D-mycaminose, D-angolosamine and D-desosamine. We additionally describe the transfer of these deoxysugars to macrolide aglycones using the glycosyl transferases EryCIII, TylMII and AngMII, which display usefully broad substrate tolerance. 相似文献
928.
A new indole alkaloid, namely malbrancheamide B (2), was isolated from the culture medium and mycelia of the ascomycete Malbranchea aurantiaca along with malbrancheamide (1). Structural elucidation of 2 was carried out by a combination of mass spectrometry (MS) and (1)H and (13)C NMR spectroscopy analyses, as well as by comparison of the NMR data with those of 1. According to the conformational studies using molecular mechanics analyses, compound 2 exists in one preferred conformation, which was optimised by density functional theory (DFT) calculations. Compound 2 is the second chlorinated indole alkaloid possessing a bicyclo [2.2.2] ring with an unusual relative configuration at C12a in the bicyclo [2.2.2] diazaoctane ring system. So far, these structural features seem to be unique for the alkaloids biosynthesised by the fungus M. aurantiaca. 相似文献
929.
Fong KH Kikuchi K Goh CS Set SY Grange R Haiml M Schlatter A Keller U 《Optics letters》2007,32(1):38-40
We design single-wall carbon nanotube (SWNT) thin-film saturable absorbers (SAs) integrated onto semiconductor distributed Bragg reflectors for mode-locking solid-state Er:Yb:glass lasers. We characterize the low nonsaturable loss, high-damage-threshold SWNT SAs and verify their operation up to a pulse fluence of 2 mJ/cm(2). We demonstrate passive fundamental continuous-wave mode locking with and without group-delay dispersion compensation. Without compensation the laser produces chirped 1.8 ps pulses with a spectral width of 3.8 nm. With compensation, we obtain 261 fs Fourier-transform-limited pulses with a spectral width of 9.6 nm. 相似文献
930.
Site-selective introduction of biotin and benzophenone probes onto ginkgolide scaffolds is described. 相似文献